1. Field of the Invention
This invention relates to a removable and reusable apparatus for safe, cost-effective upgrade or repair of in-service pipelines without the interruption of flow within such pipelines.
2. Description of Prior Art
Numerous devices are taught by the prior art for insertion of plugs or flow control valves into in-service pipelines without interrupting the flow through said pipelines. Electro-fusion as a means for securing a pipe fitting to a plastic pipe, or otherwise coupling thermoplastic pipes, is also taught by the prior art.
Jiles, U.S. Pat. No. 5,052,431, teaches a method and apparatus for sealing a gas pipe carrying gas under pressure and, if desirable, for providing a tap in the gas pipe whereby a bypass around a damaged section of the pipe may be effected. In accordance with the teachings of the '431 patent, two branching saddles are bonded by conventional means to the side of the pipe at a distance from each other. The branching saddles are provided with a cylindrical pipe stub through which plugging or tapping of the pipe is accomplished. A fixture is mounted on the pipe stubs of the branching saddles. The fixture provides a bypass for the gas flowing in the in-service pipe between the branching saddles. Once the repair is made, gas flow through the pipe between the branching saddles is restored, the pipe stubs of the branching saddles are plugged, and the fixture is removed, leaving the branching saddles and plugged cylindrical pipe stubs on the in-service pipe.
Weller et al., U.S. Pat. No. 4,883,085, teaches a method and apparatus for installing plastic fittings and line stopping mechanisms in an in-service pipeline having a stopper shaft which is used to remove a completion plug in the fitting during installation, and to control the line stopper mechanism once it is installed within the fitting. Installation of the fitting is accomplished using electric resistance fusing.
Ward, U.S. Pat. No. 3,863,667, teaches a shear disposed within a fluid tight housing permanently secured to the exterior of an in-service pipeline operable by an external actuator through an aperture in the housing. The aperture is sealed by the shear when the shear is retracted from the pipeline to permit the actuator and related components to be separated from the housing without loss of fluid from the severed pipeline. Similarly, Smith, U.S. Pat. No. 4,355,656 teaches a shear and bypass apparatus, the shear cutting the pipe for insertion of a plug and simultaneously providing flow through a bypass so that flow through the in-service pipeline is not interrupted.
Gardner, U.S. Pat. No. 3,867,964, teaches a flow control apparatus installed into an in-service pipeline having a cutter enclosed in a fluid tight housing disposed around the pipeline. The '964 patent also teaches that a pair of said apparatuses may be connected to the pipeline to provide a bypass pipe circuit.
Margrave, U.S. Pat. No. 4,552,170, teaches a valve inserted into an in-service pipeline. The valve is separable into two halves which are clamped around the pipeline. A valve handle is then rotated to drive a cutter through the line and to position an expandable seal across the line bore.
Reeves, U.S. Pat. No. 4,571,488, teaches a thermoplastic heat-fusion pipe fitting system comprising a thermoplastic heat-fusion pipe fitting with a body portion to accommodate a pipe, and a shaped portion bearing a code indicative of the amount of heat required to effect fusion of the fitting. Also provided are means for heating the fitting, means for sensing and decoding the code, and control means for regulating the amount of heat applied to the fitting.
Handa et al., U.S. Pat. No. 4,994,655, teaches an electro-fusion joint for formation of a socket-type pipe joint or a saddle-type joint. Bridgstock et al., U.S. Pat. No. 4,486,650, teaches an electro-fusion fitting for coupling thermoplastic pipe. Furthermore, Moreau et al., U.S. Pat. No. 5,138,136, teaches an electric power supply for an electrical resistive heating element suitable for construction or repair of pipe systems made from plastic material.
Although numerous prior art references teach apparatuses for insertion of pipeline accessories into in-service pipelines, they teach permanently affixing a housing or fixture to the pipeline. Consequently, the housing or fixture that remains on the pipeline may not be reused at another pipeline location and is abandoned at the repair site. Alternatively, housings which are known to be reusable generally require elaborate preparatory measures prior to initiation of line-stopping operations, such as the attachment by electrofusion of an expensive saddle fitting to the pipe, resulting in the passage of a substantial amount of time before line-stopping operations can be undertaken. Furthermore, the prior art teaches installation of pipeline elements specially adapted for use with a particular installation apparatus, thereby, prohibiting the installation of other widely used and commercially available pipe elements.